Ion concentration control



Sept. 18, 1928. 1,684,645

I. B. SMITH ET AL ION CONCENTRATION CONTROL Filed Jan. 5. 1922 CO VCA'NT'RATION OF IO KflL-I IN VEN TORS i4 ATTORNEY.

Patented S ept. 1928.

" UNITED*STA i i I A a TES PATENT OFFICE,

InvIne 3. sum, or ArrBLnn,Ann EARL A. mun, or nonnrs'rowx, mum

VANIA, ASSIGNORS .ro Lnnns a non'rnnur comrAmr, or rnInAnnLrnIA, 2mmsYLvANIA, A conronA'rIon or PENNSYLVANIA ION CONCENTRATION CONTROL.

Application filed January 3, 1922. Serial No. 528.382.

Our invention relates to the method of and apparatus for affecting to known or predetermined extent the true or primary concen- "tration of-a predetermined or selected ion or ions of or in a solution or equivalent for the purpose of procuringa pseudo or secondary ion concentration, variations in whose magnitude are accompanied by variations of potential difference greater than those accompanying the corresponding variations of the true or primary ion concentration; that 1s there is eifected greater change of voltage or potential diiference per unit change in 10]). concentration; whereby there is obtainable greater accuracy or sensitivity in determinations or measurements of or controls by variations of the true ion concentration.

In accordance with our invention the true or prima ion concentration is so modified or changdd that, in effect, it is ofiset or shifted to a more suitable or desirable portion of its potential or voltage characteristic; or so modified or changed that its potential or voltage characteristic is, in effect, suitably changed.

In accordance with our invention, to the ends aforesaid/the solution, or equivalent,

I the concentration of the selected ion or ions of which is involved, is diluted by water or by other suitable or equivalent fluid or solution, to a known or predetermined extent; or has added thereto a suitable solution of reagent of known or predetermined strength in a known or predetermined quantity to effect partial or complete neutralization; or has added thereto a solution or equivalent of or containing suitable chemical or other material producing an effect known as buffer action.v v

Our invention resides in the methods and apparatushereinafter described and claimed.

For an understanding of our methods, and for an illustration of some of the many forms our apparatus may take, reference is bad to the accompanying drawings, in which:

Fig. 1 is a characteristic curve illustrating the relations between potential differences and concentrations of acid or alkali.

Fig. 2 is a view, largelydiag'rammatic, of

" apparatus embodying and utilizable in connection with our invention.

1 Fig. 3'is a view in perspective of apparatus embodying our invention and utilizable for practicing our methods;

Referring to Fig. 1, ordinates represent potential difierences or volta es and abscissae represent concentrations 0 acid or alkali, or equ valents. On the characteristic curve the point a corresponds with neutrality, and represents the point beyond which neither acldity nor alkalinity is or can be decreased. .That part of the curve extending belowand to the left of the point a corresponds with increasing acidity, while the portiomextendmg above and tothe right of the point a corresponds with increasin alkalinity. For high acidity and high a alinity the curve flattens, or becomes parallel or nearly ar allel with the axis ofabscissae, and there ore illustrates the fact that even relatively eat changes of ion concentration in the igh acidity and high alkalinity ranges are accompanied by very small changes in potential difference or voltage. Accordingly, when determinations or measurements of or controls by ion concentration in the high acidit and high alkalinity ranges are involved, 0 y low sensitivity or accuracy are available because of the relativel small changes in potential difference or vo tage.

Assuming it is necessary to work in the high acidity range, corresponding with the lower left hand portion of the characteristic curve, greatly increased sensitivity or accuracy is obtainable by adding to the solution or equivalent, in known or predetermined amount or proportion, a suitable diluent, producing what may be termed a pseudo or secondary ion concentration lying in a range, as for example, between the points I) and a, whereby the actual determination, measurement or control is effected with, by or in response to relatively greater changes of voltage or potential difference than would occur if operating in that portion of the characteristic to the left of the region 6, the determination, measurement or control then taking into account the extent or eifect of the dilution. The diluent may be chemically pure or distilled water, or at any rate, water whose contents, if any, do not undesirably react with or afiect the solution to which added, that is, the diluent is of the same character or equivalent of that com onent of the original solution which causes the variation of the ion concentration of the original solution before dilution, whereby the potential-ion-concentration characteristic of the diluted solution corres nds with or is a continuation of the potential-ion-concentration characteristic of the undiluted or original solution. Hence, when the water content of a solution causes the variation in concentration of a selected ion, the diluent material utilized is water. Or if it be not water which causes the variation in concentration of the selected ion of the original or undiluted solution then the diluent is of the character which causes such ion concentration variation.

Or in order to operate within the range, as for example, between I; and a, any suitable solution or equivalent of reagent, of known or predetermined and referably constant strength, is added to t e solution in or at known or predetermined quantity, proportion or rate, whereby partial or complete titration or neutralization is effected and the acidity is decreased in known or predetermined amount, and the potential-ion-concentration characteristic of the partially or completely titrated or neutralized solution corresponds with or is an extension of the potentia don-concentration characteristic of the original or untreated solution.

What has-been stated as to the region of high acidit a plies equally well to the region of big a kalinity, dilution or addition of reagent for partial or complete neutralization making it possible to operate in a more suitable range of the characteristic curve, as for example, between the points a and a.

Neutralization method-Referring to Fig. 2, A is any suitable vessel or container for the solution of electrolyte E, the concentration of a selected ion or ions of which is to be determined, measured or utilized for any suitable control. Assuming, for example, that concentration of hydrogen ions is involved, the electrodes employed with the electrolyte may be a calomel half cell and a hydrogen electrode. The calomel half cell comprises a tube e having a capillary or highly restricted orifice f; and the hydrogen electrode comprises the platinum electrode 9, covered by platinum black and dis osed in a current of hydrogen gas, both t ese electrodes being Well understood in the art. R is a potentiometer resistance through which current is passed from a battery or other suitable source B, the current strength being adjustable by the variable resistance h. One terminal of the cell comprising the aforesaid electrodes immersed in or co-operating with the electrol E is connected through a switch a: an galvanometer G, having a pointer or deflecting needle 19, to the contact 2' adjustable along the resistance R, or, in some instances, connecting permanently at a predetermined point on the resistance R. The

other terminal of the cell is connected to one terminal of the resistance R. As well understood in the art, as the ion concentration of the electrolyte E varies the voltage of the cell varies, and when the Volta e of the cell is equal to the fall of potential in that part of the resistance R to the left of the point i, there is no current through the galvanometer and its pointer 19 takes zero or neutral position.

To the tank, vessel or other suitable container C is delivered through pipe 7' the entire or any suitable fraction of the solution under test, employed for control, or for any other pur ose utilized. It will be assumed that an aci solution is delivered by the ipe j, and it is delivered from the cup C t rough the pipe into the container A. It is preferred that the rate of flow of the acid solution from container C to vessel A shall be constant, such constancy being obtainable by an suitable mode or means. In the example i lustrated, constancy of flow is obtained by maintainin a constant head of solution in the vessel this being accomplished by provision of the overflow pipe m, whereby the solution in container C is maintained always at the level n. Through the pipe 0 there is delivered into the cup, tank or vessel D an alkaline solution of character suitable for reaction with the acid solution for purposes of partial or complete neutralization.

livered tllIOLW'll pipe p, controlled by the valve V, into the container A, where it mixes or is mixed with the acid solution, the mixture flowing off through the outlet or overflow ipe The vessel D is preferably providecl wit an overflow pipe 7, whereby the level s of the alkaline solution in the vessel D remains at a constant height, whereby the amount of alkaline solution delivered into the vessel A will depend upon the constant head and the extent of opening of the valve Assuming the acidity of the solution delivered through the pipe is to be so high that, as regards the characteristic of Fig. 1, it corresponds with a point lying to the left of the points b or d, the addition of the alkali reduces the acidity to such extent that the ion concentration is changed to such magnitude that the operations take place in the region between the points I) and a, and, preferably, adjacent the end or neutral .point a. Thus, where the solution is that of the product of reaction of sulphuric acid with sodium hydroxide, to wit, sodium sulphate, with a great excess of sulphuric acid present, the neutralizing or titrating agent may be sodium hydroxide, which will again yield additional sodium sulphate, and in effect shift the range of measurement along the characteristic curve toward the neutral point a, with consequent magnification of the potentials derived.

l/Vith variations in the high acidity of the solution from tank C, the amount of alkaline reagent required for producing a predetermined reduction of acidity, or, in the special The alkaline solution 15 of constant strength or concentration and is de-- case, for producing neutrality, correspondingly varies, and such variation is accomplished by the valve V operated either manually or automatically. When operated manually, the position of the contact 2' upon the resistance B may be fixed at such point that the fall of potential through the resistance It to the left of the point i'corresponds with the potential difference, Fig. 1, corresponding with the neutral or end point a, or any other point below and to the left of thepoint a, as between that point and the point In such case, with the contact '5 fixed or'stationary, the operator opens or closes the valve in such wise as to cause balance of or zero current flow through the galvanometer G, movement of the valve structure servingas an index or being readable in terms of actual acidity or ion concentration of or respectin the acid solution delivered through the pipe For example, the wheel W, which rotates with or rotates the movable valve structure, in association with the shaft It, may

have, as later explained-1n connection wit Fig. 3, index markings reading in terms of .ion concentration or. acidity, a co-acting stationary' index serving for reading purposes.

Or the valve V may be automatically operated by any suitable mechanism, one of various types of which is illustrated in Fig. 3,

, wherein there is illustrated apparatus in some respects like that disclosed in prior Letters Patent of the United States to Leeds- No. 1,125,699, January 19, 1915.

In Fig. 3, M is any suitable source of power, as an electric motor, which rotates the shaft 1, preferably at substantially-constant speed, which in turn drives the worm 2 which rotates the worm gear 3 secured upon the shaft 4. Pivoted near its upper end is a lever 5, back of which and near whose lower end on a horizontal axis is the arm 6 on each end of which is a' shoe 7 of cork or, other suitable material, frictionally engaging the rim 8 of the clutch disk or wheel 9 secured upon the rotatable shaft 10. Secured upon the shaft 4 is a cam 11, which periodically engages the lever 5 and moves'it outwardly away from the disk 9 in opposition to a spring, not shown, thereby lifting the shoes 7 free from the rim 8 of disk 9. the aforesaid spring returning the shoes 7 into engagement with rim 8 after predetermined extent of rotation of cam 11.- Upon the shaft 4 is sefleeting fleeting, measuring or indicating instrument, as for example, a alvanometer of which 20 is the movable coil or other movable or deelement which swings or deflects the needle 19 to the right or left. At opposite ends of the member 17 are the abutments 21 for limiting the deflection or swing of pointer 19. Directly above the pointer 19 and beneath which it normally freely swings are the edges 22, 22, which may be straight and horizontal as indicated, upon members 23, 23 pivoted at 24, 24, extending inwardly toward each other and leaving a gap of suflicient width between their inner ends to allow free entry or upward movement of pointer 19 when in balanced, zero or mid position, the pointer normally swinging freely between the edge 18 and the edges 22, 22. The members 23,

'23 have the downwardly1 extending arms 25,

er by the 5 rings 26.

25 biased toward each ot Attached to the lower end of the ever 5 is the triangular plate 27 carrying pins 28, 28 co-operating with the lower ends of the arms 25,25. At opposite ends of the arm 6 are the ears or lugs 29, 29 adapted to be engaged by the cams 30, 30, similar in shape and similarly positioned and secured upon the shaft 4.

Secured upon the shaft 10 is adisk or wheel 31 carrying on its periphery the resistance conductor B, of Fig. 2, for example; and bearing upon the resistance R is the station arycontact 11 of Fig. 2, for example. The disk 31 may be secured to the shaft 10 in any suitable angular relation with respect thereto by set screw 33 threaded through the hub 32, through which the shaft 10 extends. It will be understood that the disk 31 and its resistance are utilized only under certain circumstances hereinafter described, and that in some cases both resistance R and contact a are stationary and are not in any wise related to the shaft 10.

Secured upon the shaft 10 is the Worm 34 meshing with and driving the worm gear or wheel W which actuates the movable structure of the valve V through the shaft t.

A-grooved pulley or wheel 35 has a hub 36 through which the shaft 10 extends and to which the pulley 35 is secured by set screw 37. Around the wheel 35 passes the cord 38 or equivalent,which passes over idler pulleys 39 and is attached to the marker or recorder pen 40, which is moved transversely, on guides, not shown, with respect to the recorder paper P stored upon a spool 41 and having the marginal perforations 42 in which engage teeth or. pins upon the periphery of the roller 43 secured upon shaft 44 driven by the motor M through the worm 45, gear 46, shaft 47, worm 48 and gear 49.

The operation is as follows:

With the resistance R stationary, that is, separate from the movable structure of Fig. 3, as to which it is therefore assumed that the disk 31 with its resistance R is omitted,

and with the contact 2' in fixed position with respect to the resistance R, and at such position, for example, that the fall of potential through the resistance R to the left of point 71 corresponds with. the potential difference of the end or neutral point a of Fig. 1, as the acidity of the solution delivered through the pipe 70 increases or decreases, the ion concentration changes, with the result that the electro-motive-force produced by the cell whose electrolyte is E correspondingly changes, with the result that the galvanometer needle 19, Figs. 2 and 3, will deflect in the one direction or the other unless the solution E is neutral. Assuming the solution is not neutral, the needle 19 will deflect in one direction or the other, for example, toward the right in Fig. 3, and to an extent corresponding with the difference from neutral condition of the electrolyte E. The needle 19 while deflected will be clamped between the edges 18 and 22, causing the displacement of the arm 6, while the shoes 7 are lifted from the rim 8, through an angle corresponding with the extent of deflection of the needle 19. Thereafter the shoes 7 re-engage the rim 8 and thereafter one or the other of the cams will engage one or the other of the lugs 29 and rotate the arm 6 to normal position indicated, thereby rotating the shaft 10 through an angle corresponding with the departure of the solution E from neutral condition. The result is that the worm 34, through the gear 1V and shaft 25, will rotate the movable element of the valve V to change its opening in such sense as to increase or decrease the amount of alkaline solution delivered into the vessel A, the operation being in such direction or sense as will tend to eliect neutral condition. Similarly, if the change as regards neutral condition is in the opposite sense, the needle 19 will deflect in opposite direction, causing rotation of the shaft 10 in opposite direction to that above assumed and movement of the valve structure in opposite sense to that previously'assumed. The apparatus is therefore automatic in maintaining the solution E neutral, this being accomplished by varying the opening of the valve V through which the neutralizing solution flows under a preferably constant head.

As the valve structure is moved in the one direct-ion or the other, the marker 40 is moved in the one direction or the other transversely of the paper P and produces thereon a curve or record from which may be read the acidity or ion concentration of the solution delivered through the pipe 70, the calibration of the readings transversely of the paper P taking into account the extent of change or modification of the acid solution to reduce it from high acidity to sufliciently low' acidity'for operative purposes in a more suitable ran e of the characteristic curve of Fig. 1. 11 other words, while the electrodes of the cell whose electrolyte is E are producin throughout the operation electro-motiveorces corresponding with low acidities, the record upon the paper P may be interpreted in terms of true acidity or ion concentration respecting the solution delivered by the pipe k.

Accordm ly, by modifying by reagent the acidity or alkalinity of a solution in accordance with our invention, greater potential differences are available for assuring greater sensitivity and accuracy, with the record or readings, however, being directly or indirect ly in terms of the true acidity, ion concentration.

In lieu of or in addition to the production of a record as described, the wheel W, or any other member movable with the shaft 10 or the movable structure of the valve V, ma carry index markings or readings witli wh-ch co-acts a stationar index 51 whereby theremay be directly read ofi the true acidity, alkalinity or true ion concentration, the calibration of the scale 50 taking into account the ofi'settting or modification of the ion concentration from the true concentration.

While in connection with Fig. 2 it has been assumed that the valve V controls reagent oflsetting or modification of the ion concentration, it will be understood that the valve V may control the flow of solution with respect to which ion concentration is to be determined, measured or utilized for control purposes. In other words, the valve V, in lieu of controlling the pipe 12, may be inserted in and control the flow through the pipe 70, in which case the apparatus of Fig. 4 operates in manner similar to that described.

Dilution method.Referring to Fig. 2, the solution to be modified is again assumed to be delivered by the pipe is into receptacle A. For purposes of description, it will be again assumed that this is an acid solution and one, for example,-whose acidity is high. There is a constant flow of the acid solution through the pipe is, and there is provided also a constant flow of the diluent, as water, from the vessel I) through the pipe 72, the valve V in this case being either entirely omitted or given a fixed opening, whereby the ratio of diluent to acid solution remains constant. The amount of water or diluent employed is preferably in excess, and preferabl greatly in excess over the volume of the aci solution delivered through the pipe is. Changes of acidity in consequence cause greater changes in voltage produced by the cell whose electrolyte is E. The ion concentration or acidity may then be determined or measured by alkalinity or moving the contact 11 along the resistance R,

in non-automatic apparatus, to such point that the deflection of the galvanometer G is nil. Then by closing the switch 14 the voltmeter 1) is brought into circuit and its deflection will correspond with the voltage roduced by the cell, which voltage is equa l to Ill neegm the fall of potential in the resistance R to the able with or by the shaft 10, may be similarly left of the point i. The scale w of the voltcalibrated in terms of true aci ity, ion conmeter may be calibrated in terms of potential differences or'voltages, or may be calibrated directly in terms of true acidity, ion concentration, or P values; that is, in calibrating the scale 40 there is taken'into accountthe ofi'set or modification occasioned by the diluent. 1

Or, with the valve V omitted, as assumed, or if present having a constant opening, in which case the connection fromwheel W to the movable valve structure in Fig. 3 may be omitted, and by employing the resistance R upon the disk 31 and holding the contact a stationary, the apparatus of Fig. 3'will' produce a record upon the paper P of the acidity, ion concentration or P value-of the solution delivered through the pipe 70, and the record may be read or interpreted directly in terms of true acidity, ion concentration or P value. In this case also the wheel W, or any other wheel or dial movable with or by the shaft 10, may be similarly calibrated in terms of true acidity, ion concentration or P value.

Or with the valve Vpresent and operated by the shaft 10 of Fig. 3, and with resistance R stationary and contact 11 set and fixed at suitable point thereon, the amount of diluent will be automatically varied so as to obtain an ion concentration, acidity or P value corresponding with any suitable chosen point at or between the points a, b of Fig. 1. Or the valve V ma be in the ipe 70, so varying the fiow of aci solution w iile the diluent flows at constant rate. In either. event, the mechanism of Fig. 3 will produce a record on the paper P and the readingson the wheel W will be in terms of true ac1dity,1on concentration or P value.

Bet/fer method.This method may be practiced in the same manner as described in connection with the dilution method, the solution containing the bufier material or salts being contained in the vessel D andmixed with the solution delivered by the pipe k in the vessel A.

By this method the true acidity, ion concentration or P value may be read upon the voltmeter '0, Fig. 2, when the resistance R is not a part of an automatic system and when the contact 71 is moved along the resistance R by the operator.

Or with the valve V omitted, or if present, having a constant opening, in which case the connection from wheel W to the valve V 1n Fig. 3 inay be omitted, and by employing the resistance R upon the disk 31 with contact 2' stationary, the apparatus of Fig. 3 will produce a record upon the paper P of the acidity, ion concentration or P value of the solution delivered through the pipe is, and the record may be read or interpreted directly in terms of true acidity, ion concentration or P value. The wheel W, or any other wheel or dial mov- .centration or P value.

Or with the valve V present and operated by the shaft 10 of Fi 3, and with the resistance R stationary an contact e set and fixed.

at suitable ppint thereon, the amount of bufier solution W1 be automatically varied so as to obtain an ion concentration, acidity or P valuecorresponding with any suitable or chosen point. Or the valve V may be in the pipe is, so var ing the flow of acid solution while the bu er solution flows at constant rate. In either event, the mechanism of Fig. 3 will automatically control the valve V and produceja record on paper P whose readings and those on the wheel W will be in terms of true acidity, ion concentration or P4; value.

Whenever a valve, as V, is employed and 4 controlled or operated automatically as described, the efiect is a determination, measurement or control of or by ion concentration in terms of valve opening or a rate of flow oi one solution with'respect to another.

While the methods and apparatus above described involve automatic control, further or different automatic control may be efiected as follows:

In Fig. 2 F is a tank or vessel into which is delivered through the pipe 3 a solution, for example, acid, and a second' liquid or solution, as water or alkali, is delivered through the pipe z, the liquids coming into mixture in .the tank F and discharging through the outlet a. Either of the pipes y or a is controlled by a valve V whose o ening is controlled by the rotatable rod t, w ich may be driven by the wheel W of the automatic apparatus of Fig 3. In such case the valve V of Fig. 2 is omitted, or if present, has a fixed opening, and is disconnected from the automatic mechanism of Fig. 3. Where the acidity, for example, of the solution delivered by the pipe 3 into tank F varies, and it is desired to maintain a uniform acidit of thesolution delivered through the disc arge (1 the amount of water, alkali or other suitable solution delivcred through the pipe z is automatically controlled by the automatic mechansm of ig. 3

by automatically controlling the valve V the resistance B being in such case stationary and the contact 41 set fixedly at a suitable pointupon the resistance R to correspond with a desired acidity, or broadly, ion concentration of the solution delivered through the discharge a, taking into consideration, however,

tainin greater sensitivit as hereinbefore describe Some of the en product or solution in the tank F is delivered throu h the pipe 7', which may be controlled by va ve b, to the container C, as hereinbefore described, and the effect of the solution or material from container D etfects the modification, iving greater sensitivity by employing an e ectromotive-force change greater per unit change in ion concentration than would be available in the case the electrodes 7 and g were immersed in the material delivered from the tank F.

Accordingly, the end product of a mixture of suitable solutions or reagents is automatically maintained constant as to acidity, alkalinity, or in general, ion concentration, but the automatic mechanism is controlled in response to a pseudo acidity, alkalinity or ion concentration by mixing with the end product solution a diluent, reagent or buffer solution.

It shall be understood, however, that in lieu of employing the end product or solution of the tank F for mixture with a neutralizing, diluting or bufi'er solution, the valve Y may be closed, and a portion of the solution delivered by either of the pipes y or a may be delivered into the container C. In such case the automatic control is effected in response to an electro-motive-force depending upon the ion concentration of one of a plurality of the main solutions which are to come into mixture, modified by a buffer, diluting or neutralizing solution brought into mixture therewith for procuring an amplified or increased electro-motive-force.

What we claim is:

1. In the utilization of changes of ion con centration, the method which comprises producing a potential difference varying in magnitude with variations in ion concentration, magnifying the change in potential difference per unit change in ion concentration by admixing with the solution containing the-ions involved a material whose quantity bears a predetermined ratio to the quantity of sald solution and of such character as to change the ion concentration to a position on the potential ion concentration characteristic such that the potential gradient is greater than that of the unmodified solution, and utilizing the magnified potential difference to control the ion concentration of the unmodified solution.

2. In the utilization of changes of ion concentration, the method which comprises producing a potential difierence varying in magnitude with variations in ion concentration, magnifying the change in potential difference per unitchange in ion concentration by admixing with the solution containing the ions involved a material whose quantity bears a predetermined ratio tothe quantity of said solution and of such character as to change utilizing the magnified potential difference tocontrol the ion concentration of the modified solution.

3. In the utilization of changes of ion concentration, the method which comprises pro: I

ducing a potential difference varying in magnitude with variations in ion concentration, magnifying the change in potentialdifierence per unit change in ion concentration by adding to the solution containing the ions involved a reagent of such character and whose quantity bears a predetermined ratio to the quantity of said solution as to change the ion concentration to a position on the potentialion-concentration characteristic such that the potential gradient is greater than that of the unmodified solution, and utilizin the magnified potential difierence to control the ion concentration of the unmodified solution.

4. In the utilization of changes of ion concentration, the method which comprises producing a potential difference varying in magnitude with variations in ion concentration, magnifying the change in potential difference per unit change in ion concentration by addmg to the solution containing the ions involved a reagent of such character and whose quantity bears a predetermined ratio to the quantity of said solution as to change the ion concentration to a position on the potentialion-concentration characteristic such that the potential gradient is greater than that of the unmodified solution, and utilizing the magnified potential difference to control the ion concentration of the modified solution.

5. In the utilization of changes of ion concentration, the method which comprises producing a potential difference varying in magnitude with variations in ion concentration, magnifying the change in potential difference per unit change in ion concentration by addmg to the solution containing the ions involved a diluent of such character and whose quantity bears a predetermined ratio to the quantity of said solution as to change the ion concentration to a osition on the otentialion-concentration c aracteristic suc that the potential gradient is greater than that of the unmodified solution, and utilizing the magnified potential difference to control the ion concentration of the unmodified solution.

6. In the utilization of changes of ion concent-ration, the method which comprises producing a potential difference varying in magnitude with variations in ion concentration, magnifying the change in potential difference per unit change in ion concentration by adding to the solution containing the ions involved a diluent of such character and whose quantity bears a predetermined ratio to the quantity of said solution as to change the ion concentration to a 1positioiion the otentialion-concentration c aracteristic suc that the potential gradient is greater than that of the unmodified solution, and utilizing the magnified potential diilerence to control the ion concentration of the modified solution.

7. The method of increasing the sensitivity or accuracy of ion concentration determinations, which consists in flowing a solution containing the ions involved, mixing therewith a stream of solution of such charaoter as to efi'ect change of potential differenoe per unit change of ion concentration of increased magnitude between electrodes contacting with the mixture, Varying the ratio of the rate of flow of one of said solutions with respect to the rate of flow of the other to maintain a substantially predetermined difference of potential, and utilizing variations of said ratio as representative of variations of the ion concentration.

" 8. The method of increasing the sensitivity or accuracy of ion concentration determinations, which consists in flowing a solution containing the ions involved, mixing therewith a stream of solution of such character as to effect change of potential difference per unit change of ion concentration of increased magnitude between electrodes contactin with the mixture. varying the ratio of the rate of flow of one of said solutions with respect to the rate of flow of the other to maintain a substantially predetermined difference of potential, and utilizing variations of said ratio for producing a record representative of variations of the ion concentration.

7 9. The method of increasing the sensitivity or accuracy of ion concentration determina-. tions, which consists in flowing a solution containing the ions involved, mixing therewith a stream of solution of reagent of such character as to effect change of potential difference per unit change of ion concentration of increased magnitude between electrodes contacting with the mixture, varying the ratio of the rate of flow of one of said solutions with respect to the rate of flow of the other to maintain a substantially predetermined difi'erence of potential, and utilizing variations of said ratio as representative of variations of the ion concentration.

10. The method of increasing the sensitivity or accuracy of ion concentration/determinations, which consists in flowing a solution containing the ions involved, mixing therewith a stream of diluent to effect change of potential difference per unit change of ion concentration of increased magnitude between electrodes contacting with the mixture,

varying the ratio of the rate of flow of one of said streams with respect to the rate of flow of the other to maintain a substantially predetermined difference of potential, and

utilizing variations of said ratio as repre- 'sentative of variations of the ion conoentra means for producing a record controlled by i the altered potential difference.

12. Apparatus for utilizing ion concentration effects comprising means for producing a potential difference whose magnitude varies with variations in concentration of the ions of a solution, means for admixing with said solution a material of such character and in such quantity as to magnify the change of potential difierence per unit change of ion concentration to predetermined extent, and

means-controlled by the magnified potential difiercnce for producing a record of and for varying the ion concentration.

13. Apparatus for utilizing ion concentration efi'ec-ts comprising means for producing a potential difference whose magnitude varies with variations in concentration ofthe ions of a solution. and means for producinga stream of said solution inmixture with a stream of material of such character and in such quantity as to change the ion concentration and alter the change of potential diiference per unit change'o'f ion concentration.

14. Apparatus for utilizing ion concentration effects comprising means for producing a potential difference whose magnitude varies with variations in concentration of the ions of a solution, and means for producing a- -stream of said, solution in mixture witha stream of material of such character and in such quantity as to change the ion concentration and magnify the change of potential difference per unit change of ion concentraof a solution, means for admixing with said solution a material of such character and in such quantity as to magnify the change of potential difierence per unit change of ion con centration to predetermined extent, andp means controlled by the magnified potential difierence for varying the proportions of said solution and material.

16. Apparatus for utilizing ion concentrationefiects comprising means for producing a potential difierence whose magnitude varies with variations in concentration of the ions of a solution, means for admixing with said solution a material of such character and in such quantity as to magnify the change of potential difi'erence perunit change of ion concentration to predetermined extent, and means controlled by the magnified potential difierence for varying the proportions of said solution and material in accordance with changes of the concentration of said ions.

17. Apparatus for utilizing ion concentration effects comprising means for producing a potential difference whose magnitude varies with variations in concentration of the ions of a solution, means for admixing with said solution a material of such character and in such quantity as to magnify the change ofpotential difference per unit change of ion concentration to predetermined extent, and means controlled by the magnified potential diiference for varying the proportions of said solution and said material in accordance with variations of the ion concentration from a predetermined concentration.

18. Apparatus. for utilizing ion concentration effects comprising means for producing a potential difference whose magnitude varies with variations in concentration of the ions of a solution,. means for admixing with said solution a material of such character and in such quantity as to magnifiy the change of potential difierence per unit change of ion concentration to predetermined extent, and means for varying the proportions of said solution and said material in such sense and to such extent as to maintain a substantially constant otential difl'erence notwithstanding variations in concentration of said ions.

19. Apparatusfor utilizing ion concentration effects comprising means for producing a potential difl'erence whose magnitude varies with variations in concentration of the ions of a solution, means for producing a stream of said solution in mixture with a stream of material of such character and in such quantity as to change the ion concentration and alter the change of potential difference per unit change of ion concentration, and means for varying the proportions of said solution and material.

20. Apparatus for utilizing ion concentration effects comprising means for producing a potential difference whose magnitude varies with variations in concentration of the ions of a solution, means for producing a stream of said solution in mixture with a stream of material of such character and in such quantity as to change the ion concentration and alter the chan e of potential difference per unit change 0 ion concentration, and means for varying the proportions of saidsolution and materlal in accordance with changes of the concentration of said ions.

21. Apparatus for utilizing ion concentration eiiects comprising means for produc ing a potential difference whose magnitude varies with variations in concentration of the ions of a solution, means for admixing with said solution a material of such character and in such uantity asto magnify the change of potentidi difference per unit change of ion concentration to predetermined extent, means for varying the roportions of said solution and material, an mechanism controlling said third named means in response to changes in said potential difference.

22. Apparatus for utilizing ion concentration effects comprising means for producing a potential difference whose magnitude varies with variations in concentration of the ions of a solution, means for producing a stream of said solution in mixture with a stream of material of such character and in such quantity as to change the ion concentration and alter the change of potential difference per unit change of ion concentration, means for varying the proportions of said solution and material, and mechanism controlling said third named means in response to changes in said potential difference.

23. Apparatus for utilizing ion concentration efl'ects comprising means for producing a potential difference whose magnitude varies with variations in concentration of the ions of a solution, means for producing a stream of said solution in mixture with a stream of material of such character and in such quantity as to alter the change of potential difference per unit change of ion concentration, structure for varying the proportions of said solution and said material, a motor device for actuating said structure, means for coupling said structure to said motor device, and means controlled by said potential difference controlling said coupling means.

24. Apparatus for utilizing ion concentration efiects comprising means for producing a potential difierence whose magnitude varies with variations in concentration of the ions of a solution, means for producing a stream of said solution in mixture with a stream of material of such character and in such quantity as to alter the change of potential difierence per unit change of-ion concentration, structure for varying the proportions of said solution and said material, a motor device for actuating, said structure, means for coupling said structure to said motor device, and means responsive to changes in magnitude of said potential difference rendering said coupling means operative for a time commensurate with the magnitude of variation of said potential difference.

25. Ap aratus for utilizing ion concentration etiiacts comprising means for producing a potential difference Whose magnitude varies with variations in concentration of the ions of a solution, means for admixing with said solution a material of such character and in such quantity as to alter the change of memes potential difi'erence er unit change-of ion concentration, a mar er, a motor, means for coupling said motor to said marker, and means responsive to variations in magnitude of said potential difference controlling, said coupling means. 4

26. Apparatus for utilizing ion concentration efiects comprising means for producing a potential diiierence whose magnitude varies with variations in concentration of the ions of a solution, means for producing a stream ofsaid solution in mixture with a stream of material of such character and in such'quantity as to alter the chan tential difference per'unit change ion concentration, a source of voltage of fixed magnitude, a galvanometer subjected to the difierence between the voltage of said source and the voltage due to said altered solution,

structure controlling the proportions of said solution and said material, and mechanism controlled by said galvanometer controlling said structurer 27. Apparatus for utilizing ion concentration efiects comprising means for producing a potential difierence whose magnitude va ries with variations in concentration of the ions of a solution, means ior producing a stream of said solution in mixture with a stream of material of such character and in such quantity as to magnify the change of potential difierence per unit change of ion concentration, a source of voltage of fixed magnitude, a galvanometer subjected to the difierence between the voltage of said source and the voltage due to said altered solution, structure controlling the proportions of said solution and said material, and mechanism controlled by said galvanometer controlling said structure.

28. Apparatus for utilizing ion concentration efltects comprising means for producing a potential difierence whose magnitude varies with variations in concentration of the ions of a solution, means for producing a stream of said solution in mixture with a stream of material of such character and in such quantity as to alter the change of potential difierence per unit change of ion concentration, a source of voltage of fixed mag nitude, a galvanometer subjected to the difference between the voltage of said source and the voltage due to said altered solution, a marker, and mechanism controlled by said galvan'ometer controlling movement of said marker.

29. Apparatus for automatically varying the'proportions of main solutions comprising means for producing an electro-motiveforce whose magnitude varies with variations in ion concentration of the mixture of said main solutions modified by a secondary solution of such character and inisuch quantity as to efiect a change of potential difierence per unit change of ion concentration of mage of pen Apparatus for automatically varying the proportions of main solutions compris- 1 ing means for producing an electro-motiveforce whose magnitude varies with variations in ion concentration of the mixture of said main solutions modified by a secondary solu-- 7 tion of such character and in such quantity as to effect a change of potential difference per unit change of ion concentration of magnitude greater than the magnitude eiiected by the mixture of said main solutions, and means responsive to variations of magnitude of said potential diiference controlling the proportions of said main solutions.

3L Apparatus for automatically varying the proportions of main solutions comprising means for producing an electro-notiveforce whose magnitude varieswith variations in ion concentration of one of said main solutions modified by a secondary solution of such character and in such quantity as to efiect a change of potential difierence per unit change or ion concentration ofmagnitude difierent from the magnitude efiected by said one of said main solutions, and means responsive to variations of magnitude of said potential difi'erence controlling the proportions of said main solutions.

32. Apparatus for automatically varying the proportions of main solutions comprising 1 means for producing an electro-motive-force whose magnitude varies with variations in ion concentration of one of said main solutions modified by a secondary solution of such character and in such quantity as to efiect a change of potential difi'erence per unit change of ion concentrationoi magnitude greater than the magnitude eflected by said one of said main solutions, and means responsive to variations of magnitude of: said potential difference controlling the propertions of said main solutions. 7

33. The method of proportioning main solutions, which consists in producing a potential difierence dependent upon the ion concentration of the mixture of said mainsolutions modified by admixture with a secondary solution of such character and in such q uantity as to efiect a change of potential difieri ence per unit change of ion concentration 0 magnitude greater than the magnitude offected by said mixture of said main solutions, and controlling the proportions of said main solutions in response to variations in the magnitude of said potential difierence.

34. The method of proportioning 'main solutions which consists in producing a poten tial diiierence dependent upon the ion concentration of one of said main solutions modified by admixture with a secondary solupan tion of such character and in such-quantity as to effect a change of potential difference per unit change of 1on concentration of mag-,

nit-ude differing from the magnitude effected such quantit as to magnify the chan of potential di erence per unit change 0 ion concentration, and means for indicating the concentration of ions in the solution comprising a galvanometer having an index and a co-acting scale calibrated with reference to the ma cation of potential difference offected y said material and reading in terms of concentration of the ions of said solution alone. 7

In testimony whereof we havehereunto aifixed our signatures this 29th day of December, 1921.

IRVING B. SMITH. I EARL A. KEELER. 

